Turbo-generator with inlets and outlets for cooling channels in the rotor slot opening into the airgap



March 4, 1969 E. ESSEN 3,431,443

TURBO-GENERATOR WITH INLETS AND OUTLETS FOR COOLING CHANNELS IN THEROTOR SLOT OPENING INTO THE AIRGAP Filed Dec. 26, 1967 Sheet of 5 Fig.

B 0 24 Fig.3

[NVENT R. E -A42 E68 March 4, 1969 E. ESSEN 3,431,443

TURBO-GENERATOR WITH INLETS AND OUTLETS FOR COOLING CHANNELS IN THEROTOR SLOT OPENING INTO THE AIRGAP Filed Dec. 26, 1967 Sheet 2 of a INVENT 0R. FDQA w E58 m L L L u. YQ

March 4, 1969 E. ESSEN 3,431,443

TURBO-GENERATOR WITH INLETS AND OUTLETS FOR COOLING CHANNELS IN THEROTOR SLOT OPENING INTO THE AIRGAP Filed Dec. 26, 1967 Sheet 3 of 5 1 fIf V 4 4 I I Y J U/lIJ/III Fig. 6-6

A ll/ [1]) mvsm R. RU -A R 1255 N United States Patent 17,7 32/ 66 US.Cl. 310-65 6 Claims Int. Cl. H021; 1/32, 3/24 ABSTRACT OF THE DISCLOSUREIn a gas cooling turbo-generator, the rotor has cooling channels in thewinding slots and slot insulation at the slot surfaces, with a bundle ofconductors arranged in each slot. The stator core has radial air gapsopening into the air gap for conducting coolant. The coolant channels inthe winding slots have inlet and outlet openings. Each bundle ofconductors is formed of mutually insulated solid conductors gluedtogether, the bundles being separated from the slot insulation by spacerelements arranged consecutively axially and limiting in the axialdirection slot cooling channels formed between the conductor bundles andthe slot insulation.

BACKGROUND OF THE INVENTION (1) Field of the invention The presentinvention relates to a turbo-generator with inlet and outlet openingsfor cooling channels in the winding slot of the rotor opening into theair gap. A gaseous coolant is forced in known manner through the inletopening into the air gap by means of over-pressure arising due to themovement of the rotor in relation to the surrounding air, for exampledue to oblique positioning of the openings. Similarly cooling gas issucked out of the outlet openings facing the air gap.

(2) The prior art In known machines of similar type the insulationbetween said bundles of conductors and the walls of the slot consist-ssubstantially of a thick insulating casing tightly enclosing the bundleof conductors and holding it together. In order for the relatively lowpressure dilference between the inlet and corresponding outlet openingto be able to force a sufficient quantity of cooling gas through theslot, this must be cooled by means of several cooling circuits and eachcooling circuit must be so designed that the flow distance from theinlet opening to the outlet opening is relatively short. In known modernmachines with air gap intake, the cooling channels are arrangeddiagonally in relation to the bundle of conductors so that the coolinggas flows in through holes in the slot, is led on one side of an axialplane through the centre of the slot down to the bottom of the slot andthen back to the air gap through cooling channels arranged on the otherside of said axial plane. The inlet opening is situated in a zonelimited in axial direction where cooling gas is supplied to the air gapby means of radial channels in the stator and corresponding outletopenings are situated in a zone axially apart in which the cooling gasflowing from the slot is sucked into the stator core.

It is known to provide cooling channels running in the slot with thehelp of spacer elements of corrugated sheet metal between the slot walland the bundle of conductors, whereby the ridges formed in the metal runin axial direction. However, this construction necessitates a thicklayer of insulation between the bundle of conductors and the corrugatedmetal and is scarcely suitable since effective cooling can only beachieved if those conductor surfaces past which the cooling gas flowsare uninsulated, or at the most insulated with a very thin layer withrather small heat insulating capacity.

According to a more recent, known construction, the cooling channels inthe rotor are .made by punching holes in the various conductors in aconductor bundle in such a way that a certain axial displacement ofcooperating holes takes place between adjacent conductors. The maininsulation between the bundle of conductors and the core consists of athick coil insulation which surrounds the bundle and keeps theconductors together.

According to another known, rather recent version, diagonal slots aremade in the side surfaces of the bundle of conductors, for instance bymilling, which slots, together with the coil insulation surrounding thebundle of conductors, form walls in the diagonally running channels.

Both the latter constructions provide effective cooling but have thedisadvantage that the manufacturing process is so complicated andtime-consuming that a great part of the advantage gained in the form ofmore economical use of material since high-pressure fans are notrequired is counteracted by an increase in manufacturing costs.

SUMMARY OF THE INVENTION The above disadvantages are avoided by means ofthe invention which relates to a gas cooled turbo-generator comprising arotor having winding slots furnished with cooling channels and slotinsulations abutting the slot surfaces, and a bundle of conductorsarranged in each slot, and a stator surrounding the rotor, the statorcore having radial channels opening into the air gap, said channelsbeing for the supply and removal of a gaseous coolant for directlycooling said bundle of conductors, while the coolant channels in thewinding slots of the rotor are provided with inlet and outlet openings,known per se, for pressure or suction action, respectively, and ischaracterised in that said bundle of conductors consists of mutuallyinsulated solid conductors glued together and that said bundle ofconductors is separated from the walls of the slot by means of severalspacer elements of insulating material arranged axially consecutivelyand abutting the slot insulation, in which said spacer elements in axialdirection at least partly limit a number of first and second slotcooling channels arranged in axial sequence and formed between theconductor bundle and the slot insulation, and that said first slotcooling channels are in connection with the inlet openings and saidsecond slot cooling channels with the outlet openings, said first andsecond slot cooling channels being connected in pairs with each otherand that said spacer elements are glued to the side surfaces of thebundle of conductors and that the only or substantially solid insulationbetween the core and the side surfaces of the conductor bundle notcovered by said spacer elements consists of said slot insulation.

In a turbo-generator according to the invention great use has been madeof the fact that with modern glue and adhesion processes it is possibleto effect extremely reliable mechanical connections between metalsurfaces and between metal and non-metallic substances. Experiment hasled to the conclusion that by means of internal glueing of theconductors a conductor bundle in a turborotor obtains such greatrigidity that most of the surfaces facing the slot walls may be withoutsupport against the slot walls, assuming that the spacer elementsbetween the conductor bundle and slot walls are glued to the conductorbundle so that they with certainty retain the correct position duringthe action of centrifugal forces and during movement caused byalterations in temperature. By exploiting this fact in a machineaccording to the invention the cooling channels in the rotor slot can beshaped in such a way that they are suitable for a rotor with air gapintake since the total channel cross section will be relatively largewhile at the same time an acceptable value is maintained for the copperfilling factor of the slot. Since the parts of the conductor bundlebetween said spacer elements do not require a casing to keep themtogether, and since the slot insulation is dimensioned to provide atleast the main part of the solid insulation of the conductor bundle fromthe core, the copper surfaces not covered by the spacer elements havedirect contact with the cooling gas flowing past, or contact through athin layer, for example a layer of varnish, having rather small heatconducting capacity.

In a turbo-generator according to the invention the rotor winding can bemanufactured with very low manufacturing costs in comparison with knownturbo-rotors with air gap intake, since the conductors can be made withsolid, rectangular cross section, without punching or milling.

BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will bedescribed with reference to the accompanying drawings where FIGURE 1shows an axial section through a turbo-generator according to theinvention and illustrates the general principle for a generator with airgap intake. The flow direction of the coolant is shown here, as well asin the other figures, with the help of arrows. FIGURE 2 shows an axialsection through the winding slot of the rotor; FIG. 3 shows the windingslot and the wound conductor bundle in radial view, elements lyingradially outside of the conductor bundle and spacer elements beingomitted; FIG. 4 shows in radial View a part of the radial surface; FIG.5 and FIG. 6 show the cross-sections on the lines BB and C-C,respectively, of FIG. 2.

FIGURES 7, 8 and 9 show the shape of the cooling channels in anotherembodiment of the invention. FIG- URE 7 shows a radial view of a rotorslot with conductor bundle and spacer elements with the slot wedge andthe insulation inside removed. FIGURE 8 shows an axial section along theline DD in FIGURE 7 and FIGURE 9 shows the slot in cross section alongthe line EE in FIGURE 8.

Another embodiment is showns in FIGURES 10, ll, 12 and 13, where FIGURE10 shows a winding slot in radial view with the slot wedge removed.FIGURES 11 and 12 show axial sections along the lines GG and HH,respectively in FIGURE 10. FIGURES l3 and 14 illustrate details of theinsulation.

In FIG. 1 the rotor is designated 1 and the stator 2. Cooling gas flowsfrom the inlet frames 3 radially outside the stator through radialchannels, not shown in FIGURE 1, to the feeding-in Zones in the air gap.The supply openings for cooling channels in the rotor slot are alsosituated here.

In a corresponding manner radial stator channels lead from outlet Zonesin the air gap to the outlet chamber 5 radially outside the stator core.

FIGURES 2, 3, 4, 5 and 6 Show an embodiment of the invention where saidspacer elements are formed by surrounding with large pitch the conductorbundle with a thick, insulating, essentially helical tape wound with alarge pitch, the width of which tape is only a fraction of the pitch.

In the drawings 6 designates a rotor slot with slot insulation 7. Theslot 6 contains a bundle 8 of conductors which are insulated from eachother and internally glued so that the bundle 8 forms a stiff and solidunit.

The necessary insulation for the core is effected substantially by theslot being provided with a strong and effective slot insulation andfurthermore by the gap between the bundle 8 and slot insulation 7 beingtaken up by insulating spacer elements 9 and cooling channels 20, 22,25, 26 formed by said spacer elements and having an insulating coolantflowing through them.

The spacer element 9 consists of the parts of a relatively thick,tape-shaped insulation parallel with the walls of the slot, which iswound with a high pitch and surrounds the bundle of conductors 8shown inFIGURES 2 and 3and is glued to the conductor bundle. If the centrifugalforces are great it may be suitable to make the helical insulation bodyof thin, leafed, tape-shaped parts which are relatively short, andarrange ends projecting from these between the conductors in the bundleso that the helical insulating body is anchored. The slot wedge 11 isshaped the same for all slots and is provided with inlet openings 12 andoutlet openings 13.

Between the slot wedge 11 and the conductor bundle 8 are several fillingbodies 14, having a thickness approximately the same as the thickness ofthe tape surrounding said conductor bundle. The parts of the tapebetween the wedge and the conductor bundle are designated 27.

The inlet openings 12 are arranged in pairs in direct connection with aparallelepipedic cooling channel 20 for in-fiowing coolant, whichchannel comprises a space limited between the conductor bundle and theslot insulation of one slot wall and by the tape parts 9 runningobliquely along the slot walls. The coolant is also led from the inletopenings 12 through tangentially running distribution channels 21 andinto the parallelepipedic space 22 between the conductor bundle and theother slot wall. The space 22 thus also comprises a cooling channel forin-fiowing coolant.

The spacer elements 9 are joined to each other at the bottom of the slotby spacer elements 23 consisting of the same continuous tape as theabove-mentioned spacer elements. The space between the bottom of theslot and the conductor bundle is consequently divided into several,elongated spaces 24 arranged axially consecutively. These are intendedto lead coolant in a transverse direction and in this way form aconnection between cooling channels on both sides of the conductorbundle.

The cooling channels 20 and 22 connected to the inlet openings 12 areconnected by individual channels 24 to cooling channels 25 and 26,respectively, for out-going coolant, the latter channels also beingformed by spaces with oblique parallelepipedic shape and limited in acorresponding way as the channels 20 and 22.

In the embodiments shown in FIGURES 7, 8 and 9 yokes 16 of insulatingmaterial are used as spacer elements between the conductor bundle andthe slot surfaces provided with slot insulation instead of theabove-mentioned insulating tape. The yokes 16 have a rectangular partwhich is glued to one side of the conductor bundle 8 and a triangularpart 18 which is glued to the other side. An intermediate,trapezium-shaped part 19 forms the spacer element between the conductorbundle and the slot bottom. Contrary to the embodiments of the inventionshown in FIGURES 2, 3, 4, 5 and 6 the coolant flowing in through asupply opening 12 is not distributed on both sides of the conductorbundle between the inlet opening 12 and the bottom of the slot. Afterthe flow of cooling air has passed the connection channels in the bottomof the slot formed between the yoke parts 19, it flows out through theoutlet openings 13. The cooling channels connected to the inlet openings12 are situated only on one side of the slot and those connected to theoutlet openings 13 are situated only on the other side of the slot.

The embodiment shown in FIGURES l0, l1 and 12 differ from thosedescribed above since the coolant flows through the coolant channels ofthe slot without passing from one side to the other of the slot. In thesame way as in FIGURE 3 the symbol 6) designates an inlet opening andthe symbol (9 an outlet opening. As spacer elements between theconductor bundle 8 and slot walls provided with particularly strong slotinsulation, tongues 31 of insulating material are used, which tonguesare glued to the side surfaces of the glued conductor bundle. Thetongues 31 may with advantage be made in one piece with an insulatingspacer between the slot wedge and the conductor bundle. A constructionelement formed in this way can suitably be made of several layers ofglass fibre cloth baked in cured resin, each layer being given the shapeshown in FIGURE 13, and the tongues 33 are bent before curing to formright angles with the longitudinal part 32 acting as upper insulation ofthe slot.

When the centrifugal forces are so great that an attachment elfectedsolely by means of glueing the tongues 31 is not considered sufficient,these can be made, as indicated in radial section in FIGURE 14 where 34designates laps of insulating material in the form of fabric or foilwhich are held together by means of a plastic material. The laps havedifferent lengths in radial direction and are shaped with folded-inparts 35 which are anchored at various points by pressing them betweentwo adjacent conductors in the conductor bundle 8.

I claim:

1. Gas cooled turbo-generator comprising a rotor having winding slotsfurnished with cooling channels and slot insulation abutting the slotsurfaces, and a bundle of conductors arranged in each slot, and a statorsurrounding the rotor, the stator core having radial channels openinginto the air gap, said channels being for the supply and removal of agaseous coolant for directly cooling said bundle of conductors, whilethe coolant channels in the winding slots of the rotor are provided withinlet and outlet openings for pressure or suction action, respectively,characterized in that said bundle of conductors comprises mutuallyinsulated solid conductors glued together and that said bundle ofconductors is separated from the slot insulation by means of severalspacer elements of insulating material arranged axially consecutivelyand abutting the slot insulation, wherein said spacer elements at leastpartly limit in the axial direction a number of first and second slotcooling channels arranged in axial sequence and formed between theconductor bundle and the slot insulation, and that said first slotcooling channels are in connection with the inlet openings and saidsecond slot cooling channels with the outlet openings, said first andsecond slot cooling channels being connected in pairs with each other,and that said spacer elements are connected to the side surfaces of thebundle of conductors and that substantially the only solid insulationbetween the core and the side surfaces of the conductor bundle notcovered by said spacer elements consists of said slot insulation.

2. Gas cooled turbo-generator according to claim 1, characterized inthat said spacer elements constitute sections of an insulating tapewound helically around said conductor bundle with a pitch which isseveral times greater than the Width of the tape, said first and secondslot cooling channels communicating with each other by means ofconnection channels formed between the bottom of the slot and theconductor bundle and limited in an axial direction by said tape.

3. Gas cooled turbo-generator according to claim 1, characterized inthat said spacer elements comprise a plurality of yokes arranged axiallyconsecutively, each of which is glued by one leg to each side of thebundle of conductors, the central part of the yoke lying between thebundle of conductors and the bottom of the slot, said first and secondslot cooling channels communicating with each other by means ofconnection channels axially limited by said central parts.

4. Gas cooled turbo-generator according to claim 3, characterized inthat the length of one leg of the 'yoke is substantially equal to theheight of the slot, whereas the other leg is considerably shorter andsubstantially triangular in shape.

5. Gas cooled turbo-generator according to claim 1, characterized inthat said spacer elements comprise tongues of insulating materialarranged axially consecutively between one wall of the slot and saidbundle of conductors and several tongues arranged in a similar mannerbetween the other wall of the slot and the bundle of conductors, thetongues having a length which is less than the height of the slot andbeing glued to the upper part of the bundle of conductors, saidcommunicating slot cooling channels being arranged at the same side ofthe conductor bundle.

6. Gas cooled turbo-generator according to claim 5, characterized inthat each tongue has several laps of thin insulating material which areglued to each other, several laps in each tongue being shaped withdifi'erent lengths of their radially oriented parts, and the lower endsof these tongues extending between two adjacent conductors in theconductor bundle.

References Cited UNITED STATES PATENTS 3,265,912 8/1966 Baudry 310-592,791,707 5/1957 Willyoung 310-61 2,728,001 12/1955 Gunthardt 3l06l2,702,870 2/1955 Norris 310-61 XR 2,043,120 6/1936 Punga et al. 31061563,379 7/1896 Jelfcrson 310-215 FOREIGN PATENTS 834,232 3/1957 GreatBritain. 286,427 3/ 1928 Great Britain. 1,143,917 9/1961 Germany.

MILTON O. HIRSHFIELD, Primary Examiner.

M. O. BUDD, Assistamt Examiner.

